Various types of lids for sealing the open ends of containers have been developed. It is desirable that a container lid interlock tightly onto the container it is sealing so as to be able to withstand movement and jarring without coming loose. Additionally, the lid should be capable of supporting the weight of containers stacked on top of it and it should be reusable and relatively simple to open.
U.S. Pat. No. 3,770,156 to Yates, Jr., discloses a tamperproof plastic closure attachable to the rim of an open-ended container, the closure having a flexible peripheral outer leg including a plurality of slots and a continuous lip below the slots. A bead projecting from the inner surface of the outer leg interlocks with a bead extending outward from the container rim to hold the lid onto the container. To remove the container, the lip is cut below the slots, dividing the outer wall into individual sections, so that the outer wall can be pivoted upward, thus pivoting the bead out of locking engagement with the leg of the rim.
U.S. Pat. No. 3,532,244 to Yates, Jr., discloses a plastic closure having a U-shaped channel which sealingly engages the rim of an open end of a container. The U-shaped channel has an upper wall and contains a plurality of flanges which extend downward from the upper wall of the channel and contact the rim, thereby creating a liquid-tight seal, when the closure is mounted on the container. The rim includes an annular ridge which directs the flanges to either side of the rim in order to create a tight seal and prevent the flanges from being crushed.
U.S. Pat. No. 3,519,163 to Bardell discloses a plastic container lid for shipping containers. The lid comprises a central top wall and a U-shaped channel extending about the periphery of the top wall. The channel includes an inner wall, an outer wall and an integral top section which connects the inner and outer flanges. Interlocking means are provided on the interior surface of the outer wall which lockingly engage the side wall structure of the container. Release means are provided which are at least one vertically-oriented tear line formed in the outer flange for separating the lower portion of the outer flange into two or more separate sections. The outer flange is separated by slitting the tear line with a screwdriver or the like. Afterwards, the closure can be removed from the container body.
U.S. Pat. No. 3,515,306 to Roper et al. discloses a container with cover and hidden cover release formed onto the container. The cover includes a center wall and a U-shaped edge portion extending about the center wall for mounting the cover onto the rim of the container. The outer surface of the container wall has an annular deflection rib and an annular engagement rib. The end of a screwdriver can be wedged between the deflection rib and the outer wall of the container with its shaft resting against the engagement rib. The user opens the container by pressing the screwdriver handle towards the container wall, whereby the engagement rib acts as a lever, and the end of the screwdriver pushes the outer flange of the cover out of sealing engagement with the container rim.
U.S. Pat. No. 3,474,928 to Hurtt discloses a container having snap fastening means. The rim of the container has an outwardly extending rectangular bead extending therefrom which is engaged by a generally U-shaped channel extending along the perimeter of the closure. The center portion of the closure is offset from the U-shaped channel so that it fits within the cavity defined by the side wall of the container thereby strengthening it. Locating ribs are formed on the top of the container to position containers during stacking.